These images are a composite of separate exposures acquired by the ACS and WFC3 instruments on the Hubble Space Telescope. Several filters were used to sample narrow wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are:
Blue: ACS/WFC F435W+F475W+F606W+F625W
Green: ACS/WFC F775W+F814W+F850LP
Red: WFC3/IR F105W+F110W+F125W+F140W+F160W

Acting as a “natural telescope” in space, the gravity of the extremely massive foreground galaxy cluster MACS J2129-0741 magnifies, brightens, and distorts the far-distant background galaxy MACS2129-1, shown in the top box. The middle box is a blown-up view of the gravitationally lensed galaxy. In the bottom box is a reconstructed image, based on modeling, that shows what the galaxy would look like if the galaxy cluster were not present. The galaxy appears red because it is so distant that its light is shifted into the red part of the spectrum.